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      <title>JVM类加载机制 - 交互式测验</title>
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        .quiz-body {
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        .option-item:hover {
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        .option-item.selected {
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            border-color: #4a90e2;
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        .quiz-footer {
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          display: flex;
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          align-items: center;
          min-height: 65px; /* Reserve space */
        }

        .nav-btn {
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          color: white;
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          border-radius: 8px;
          padding: 10px 20px;
          font-size: 16px;
          font-weight: 500;
          cursor: pointer;
          transition: background-color 0.2s ease, transform 0.2s ease;
          box-shadow: 0 4px 12px rgba(0,0,0,0.15);
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        .nav-btn:hover {
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        .nav-btn:disabled {
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        .result-box {
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        .final-score-container h2 {
            margin-top: 0;
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            display: flex;
            justify-content: center;
            gap: 20px;
            margin-bottom: 40px;
            flex-wrap: wrap;
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        .score-card {
            background-color: #f8f9fa;
            border-radius: 12px;
            padding: 20px;
            width: 180px;
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            border: 1px solid #e9ecef;
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            font-weight: 500;
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            font-size: 16px;
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        .score-details td {
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        .score-details td:last-child {
            text-align: right;
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            font-size: 15px;
            line-height: 1.6;
            display: none; /* 默认隐藏 */
        }
      </style>
    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>JVM类加载机制 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
                    </div>
                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
                    </div>
                    <div id="result-container"></div>
                    <div id="hint-container" class="hint-container"></div>
                </div>
                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
                  <button id="hint-btn" class="nav-btn" style="background-color: #ffc107; color: #333; box-shadow: 0 4px 12px rgba(255,193,7,0.3);">提示</button>
                  <button id="next-btn" class="nav-btn">下一题</button>
                </div>
            </div>
          </div>
      </div>

      <script>
        const quizData = [
  {
    "question": "在JVM类加载生命周期中，对于代码 `static int x = 10;`，在“准备 (Preparation)”阶段，变量 `x` 的值是什么？",
    "options": [
      "未定义，此时仅分配内存",
      "10，即其最终的初始值",
      "null",
      "0，即int类型的默认值"
    ],
    "correctAnswerIndex": 3,
    "explanation": "在准备阶段，JVM会为类的静态变量分配内存并将其初始化为数据类型的默认值。对于int类型，其默认值为0。将`x`赋值为10的操作是在随后的“初始化 (Initialization)”阶段，通过执行<clinit>方法完成的。",
    "source": "文档中「类加载的生命周期」->「3. 准备（Preparation）」部分",
    "hint": "准备阶段的主要任务是为静态变量分配内存并设置其“默认”初始值，而不是代码中显式赋予的值。"
  },
  {
    "question": "JVM的双亲委派模型（Parent Delegation Model）最核心的设计目的是什么？",
    "options": [
      "实现类的热加载和动态部署",
      "提升类加载的性能，实现并行加载",
      "确保核心类库的安全性，避免重复加载",
      "允许开发者自由替换JDK的核心API"
    ],
    "correctAnswerIndex": 2,
    "explanation": "双亲委派模型的核心优势在于：第一，避免类的重复加载，因为父加载器已经加载过的类，子加载器无需再次加载。第二，保证了Java核心库的安全性，所有加载请求最终都会委派到顶层的启动类加载器，这可以防止用户自定义的同名类（例如`java.lang.String`）替换掉系统核心类，从而保障了JVM的稳定运行。",
    "source": "文档中「双亲委派模型」->「1. 模型概述」部分",
    "hint": "思考一下，如果没有这个模型，我们是否可以自己写一个`java.lang.String`类来覆盖JDK的原始类？"
  },
  {
    "question": "以下哪种类加载器（ClassLoader）主要负责加载位于 `<JAVA_HOME>/lib` 目录下的Java核心类库（如 `rt.jar`）？",
    "options": [
      "应用类加载器 (Application ClassLoader)",
      "扩展类加载器 (Extension ClassLoader)",
      "自定义类加载器 (Custom ClassLoader)",
      "启动类加载器 (Bootstrap ClassLoader)"
    ],
    "correctAnswerIndex": 3,
    "explanation": "启动类加载器（Bootstrap ClassLoader）是JVM的顶层加载器，由C++实现，负责加载Java最核心的类库，例如`java.lang.*`等，它们通常位于`<JAVA_HOME>/lib`目录下。",
    "source": "文档中「类加载器（ClassLoader）」->「2. 类加载器的分类」部分",
    "hint": "哪一个类加载器是JVM体系的“根”，并且无法直接被Java代码获取到？"
  },
  {
    "question": "关于 `Class.forName(String name)` 和 `ClassLoader.loadClass(String name)` 两种动态加载类的方式，它们之间的关键区别是什么？",
    "options": [
      "`Class.forName()` 会执行类的静态初始化块，而 `ClassLoader.loadClass()` 默认只加载类而不进行初始化。",
      "`ClassLoader.loadClass()` 速度更快，因为它跳过了验证阶段。",
      "`Class.forName()` 不遵循双亲委派模型，而 `ClassLoader.loadClass()` 遵循。",
      "只有 `Class.forName()` 能够加载应用 classpath 之外的类。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "这是动态加载中一个非常重要的区别。`Class.forName()` 在加载类之后，会立即对类进行初始化，即执行静态变量赋值和静态代码块。而 `ClassLoader.loadClass()` 的默认行为是只完成“加载”这一步，将类的字节码载入内存，但不会触发初始化，直到该类被首次主动使用。",
    "source": "文档中「类加载的三种方式」->「2. 动态加载」部分",
    "hint": "文档中提到一个方法会“加载指定类并执行其静态代码块”，而另一个方法“仅加载类，不执行静态代码块”。"
  },
  {
    "question": "当Java应用抛出 `NoClassDefFoundError` 时，最可能的原因是什么？",
    "options": [
      "在调用 `Class.forName()` 时，类路径（classpath）配置错误，导致找不到对应的.class文件。",
      "类的编译版本高于当前运行环境的JVM版本。",
      "类的.class文件在编译时存在，但在运行时由于某种原因（如未部署或在初始化时出错）导致无法加载。",
      "试图将一个对象强制转换为一个不兼容的类类型。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "`NoClassDefFoundError` 是一个错误（Error），它表示JVM在编译时能够找到这个类，但在运行时却找不到该类的定义了。这通常发生在两种情况下：1. 类的.class文件在物理上确实丢失了（例如，打包时遗漏）。2. 该类在“初始化”阶段执行静态代码块时抛出了异常，导致类初始化失败。",
    "source": "文档中「类加载的常见问题」->「5. 类定义不匹配（NoClassDefFoundError）」部分",
    "hint": "这个错误与`ClassNotFoundException`的关键区别在于，前者涉及的类在“编译时”是存在的。"
  },
  {
    "question": "在类加载生命周期中，“解析 (Resolution)”阶段的核心任务是什么？",
    "options": [
      "为类的静态变量分配内存并设置默认值。",
      "执行类的静态代码块（`<clinit>`方法）。",
      "将常量池中的符号引用替换为直接引用（内存地址）。",
      "检查字节码文件格式是否符合JVM规范。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "解析阶段是连接过程的一部分，它的主要工作是将类、接口、字段和方法的符号引用转换为直接引用。符号引用是一种逻辑上的引用，而直接引用是直接指向目标的指针或内存地址。这个过程为后续的执行做好了准备。",
    "source": "文档中「类加载的生命周期」->「4. 解析（Resolution）」部分",
    "hint": "这个阶段是将代码中的“名字”（比如方法名）和它在内存中的“实际位置”关联起来的过程。"
  },
  {
    "question": "实现Java热加载（Hot Loading）机制，允许在不重启应用的情况下更新代码，通常依赖于以下哪项技术？",
    "options": [
      "修改JVM启动参数以开启热加载模式。",
      "利用反射API直接修改已加载类的内存结构。",
      "创建新的自定义类加载器实例来加载新版本的类文件。",
      "操作系统提供的文件监控和自动替换功能。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "JVM通过“类全限定名 + 加载它的ClassLoader实例”来保证类的唯一性。因此，要加载一个已存在类的新版本，标准做法是创建一个全新的ClassLoader实例来加载新的.class文件。这样，尽管类名相同，但由于ClassLoader实例不同，JVM会将其视为一个全新的类，从而实现了类的替换和热加载。",
    "source": "文档中「类加载与热加载」->「3. 类加载与热加载的关系」部分",
    "hint": "JVM如何判断两个同名类是否为同一个类？答案藏在类的唯一性标识中。"
  }
];
        console.log("Quiz Data:", JSON.parse(JSON.stringify(quizData))); // 添加这行用于调试，以可展开的JSON格式输出
        
        let currentQuestionIndex = 0;
        let score = 0;
        // 存储每个问题的回答状态
        const userAnswers = new Array(quizData.length).fill(null); 

        const questionTextEl = document.getElementById('question-text');
        const optionsListEl = document.getElementById('options-list');
        const resultContainerEl = document.getElementById('result-container');
        const quizContentEl = document.getElementById('quiz-content');
        const progressIndicatorEl = document.getElementById('progress-indicator');
        const prevBtn = document.getElementById('prev-btn');
        const nextBtn = document.getElementById('next-btn');
        const hintBtn = document.getElementById('hint-btn');
        const hintContainerEl = document.getElementById('hint-container');

        function loadQuestion() {
          resultContainerEl.innerHTML = '';
          optionsListEl.innerHTML = '';
          hintContainerEl.style.display = 'none'; // 隐藏提示
          
          if (currentQuestionIndex >= quizData.length) {
            showFinalScore();
            return;
          }

          updateProgress();

          const currentQuestion = quizData[currentQuestionIndex];
          questionTextEl.textContent = `(${currentQuestionIndex + 1}/${quizData.length}) ${currentQuestion.question}`;
          
          currentQuestion.options.forEach((optionText, index) => {
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            li.className = 'option-item';
            li.textContent = optionText;
            li.dataset.index = index; // Store index in a data attribute
            // 如果这道题已经回答过，恢复状态
            if (userAnswers[currentQuestionIndex] !== null) {
                if (index === userAnswers[currentQuestionIndex]) {
                    li.classList.add('selected');
                }
            }
            optionsListEl.appendChild(li);
          });

          // 如果已经回答过，直接显示结果
          if (userAnswers[currentQuestionIndex] !== null) {
              const isCorrect = userAnswers[currentQuestionIndex] === currentQuestion.correctAnswerIndex;
              showResult(isCorrect, currentQuestion);
          }
          
          updateNavigationButtons();
          updateProgress();
        }

        function selectOption(optionIndex) {
            userAnswers[currentQuestionIndex] = optionIndex;
            const currentQuestion = quizData[currentQuestionIndex];
            const isCorrect = optionIndex === currentQuestion.correctAnswerIndex;

            // 重新计算分数
            score = userAnswers.reduce((acc, answer, index) => {
                return answer === quizData[index].correctAnswerIndex ? acc + 1 : acc;
            }, 0);

            showResult(isCorrect, currentQuestion);
            updateNavigationButtons();
        }
        
        function updateProgress() {
            const answeredQuestions = userAnswers.filter(answer => answer !== null).length;
            const progressPercentage = (answeredQuestions / quizData.length) * 100;
            progressIndicatorEl.style.width = `${progressPercentage}%`;
        }
        
        function updateNavigationButtons() {
            prevBtn.style.display = 'block';
            nextBtn.style.display = 'block';
            hintBtn.style.display = 'block'; // 显示提示按钮

            prevBtn.disabled = currentQuestionIndex === 0;
            nextBtn.disabled = false; // 最后一题时，下一题按钮不禁用，而是用于显示报告
            nextBtn.textContent = (currentQuestionIndex === quizData.length - 1) ? '查看报告' : '下一题';
            
            // 如果当前问题没有提示，则禁用提示按钮并隐藏提示内容
            if (!quizData[currentQuestionIndex].hint) {
                hintBtn.disabled = true;
                hintContainerEl.style.display = 'none';
                hintContainerEl.textContent = ''; // 清除旧的提示内容
            } else {
                hintBtn.disabled = false;
            }
        }

        function showResult(isCorrect, questionData) {
            resultContainerEl.innerHTML = ''; // 清空之前的结果
            const resultBox = document.createElement('div');
            resultBox.className = `result-box ${isCorrect ? 'correct' : 'incorrect'}`;
            
            let html = `<h3>${isCorrect ? '回答正确！' : '回答错误'}</h3>`;
            if (!isCorrect) {
                html += `<p><strong>正确答案是：</strong> ${questionData.options[questionData.correctAnswerIndex]}</p>`;
            }
            html += `<div class="explanation-text">${questionData.explanation}</div>`;
            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
            resultBox.innerHTML = html;
            resultContainerEl.appendChild(resultBox);

            // 禁用所有选项的点击事件，并高亮正确/错误答案
            Array.from(optionsListEl.children).forEach((child, index) => {
                child.style.pointerEvents = 'none';
                // 高亮正确答案
                if (index === questionData.correctAnswerIndex) {
                    child.classList.add('correct'); // 需要添加CSS样式
                    child.style.backgroundColor = '#d4edda';
                    child.style.borderColor = '#c3e6cb';
                }
                // 如果选错了，高亮错误选项
                if (!isCorrect && index === userAnswers[currentQuestionIndex]) {
                    child.classList.add('incorrect'); // 需要添加CSS样式
                    child.style.backgroundColor = '#f8d7da';
                    child.style.borderColor = '#f5c6cb';
                }
            });
        }

        function goToNextQuestion() {
            if (currentQuestionIndex < quizData.length - 1) {
                currentQuestionIndex++;
                loadQuestion();
            } else {
                showFinalScore();
            }
        }

        function goToPreviousQuestion() {
            if (currentQuestionIndex > 0) {
                currentQuestionIndex--;
                loadQuestion();
            }
        }
        
        function showHint() {
            const currentQuestion = quizData[currentQuestionIndex];
            if (currentQuestion.hint) {
                hintContainerEl.textContent = currentQuestion.hint;
                hintContainerEl.style.display = 'block';
            } else {
                hintContainerEl.style.display = 'none';
            }
        }

        function showFinalScore() {
            document.querySelector('.quiz-body').style.display = 'none';
            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  